Selecting one of multiple redundant network access points on a node within an industrial process control network

Abstract

A method and network access point selection logic are described for a redundantly connected industrial LAN node including at least primary and backup network access points. Network connectivity is determined by a redundantly connected node by testing connectivity between the node's primary and backup physical network access points. Upon detecting a loss of connectivity between the redundant node's primary and backup network access points, the node executes access point selection logic, based upon tests of connectivity between the redundantly connected (primary and backup) network access points and a set of nodes on the LAN, to select a preferred/primary one of the redundant access points. Thereafter, the redundantly connected node binds its connections according to primary and backup designations for its redundant network access points.

1. A method, performed by a computer including a physical computer-readable medium including computer-executable instructions, for managing a set of network access points maintained by a single redundantly connected node on an industrial local area network (LAN) comprising the steps of:
 primarily testing bi-directional communicative connectivity, via the LAN, between a primary and a backup redundant network access point of the set of network access points; 
 secondarily testing, upon determining loss of communicative connectivity between the primary and backup network access points, connectivity between the set of network access points and a set of nodes on the LAN to which the redundantly connected node previously communicated; 
 designating a current primary network access point based upon results of the secondarily testing step; and 
 binding a first set of connections to the current primary network access point, wherein the first set of connections are re-bound to a newly designated current primary network access from a previous primary network access point in the event that the current primary network access point specified during the designating step differs from a previously designated primary network access point. 
 
     
     
       2. The method of  claim 1  wherein the secondarily testing step comprises determining a number of responses received by each one of the set of network access points and, upon detecting a first tie in the number of received responses after detecting loss of connectivity during the primarily testing step, designating a new primary network access point during the designating step in response to detecting the first tie. 
     
     
       3. The method of  claim 2  wherein the designating a new primary network access point step is performed only in response to detecting the first tie after detecting a loss of bi-directional connectivity between primary and backup redundant network access points during the primarily testing step. 
     
     
       4. The method of  claim 1  wherein the secondarily testing step comprises sending test request messages to a set of most recently accessed nodes on a network. 
     
     
       5. The method of  claim 4  wherein the set of nodes receiving request messages are determined by accessing a most recently used address list. 
     
     
       6. The method of  claim 4  wherein an odd number of secondary test request messages are sent out by the primary and backup redundant network access points. 
     
     
       7. The method of  claim 1  wherein the binding step is transparent to applications. 
     
     
       8. The method of  claim 7  wherein the primarily and secondarily testing steps are carried out transparent to applications. 
     
     
       9. The method of  claim 7  wherein the primarily and secondarily testing steps are carried out transparent to network layer processes. 
     
     
       10. The method of  claim 1  wherein the LAN incorporates ETHERNET protocols. 
     
     
       11. The method of  claim 1  wherein the primarily testing step comprises sending a request message between from the primary network access point and the backup network access point and receiving a reply message within a time period. 
     
     
       12. The method of  claim 1  wherein the designating the current primary network access point is based upon tallied responses by the set of nodes, to which the redundantly connected node previously communicated, to test requests issued via the primary and backup network access points, respectively. 
     
     
       13. The method of  claim 1  wherein the primarily and secondarily tests are carried out via logical link control layer communication protocol components. 
     
     
       14. A computer-readable medium including computer executable instructions for facilitating managing a set of network access points maintained by a single redundantly connected node on an industrial local area network (LAN), the computer executable instructions facilitating performing, by the single redundantly connected node;
 primarily testing bi-directional communicative connectivity, via the LAN, between a primary and a backup redundant network access point of the set of network access points; 
 secondarily testing, upon determining loss of communicative connectivity between the primary and backup network access points, connectivity between the set of network access points and a set of nodes on the LAN to which the redundantly connected node previously communicated; and 
 designating a current primary network access point based upon results of the secondarily testing step; and 
 binding a first set of connections to the current primary network access point, wherein the first set of connections are re-bound to a newly designated current primary network access from a previous primary network access point in the event that the current primary network access point specified during the designating step differs from a previously designated primary network access point. 
 
     
     
       15. The computer-readable medium of  claim 14  wherein the secondarily testing step comprises determining a number of responses received by each one of the set of network access points and, upon detecting a first tie in the number of received responses after detecting loss of connectivity during the primarily testing step, designating a new primary network access point during the designating step in response to detecting the first tie. 
     
     
       16. The computer-readable medium of  claim 15  wherein the designating a new primary network access point step is performed only in response to detecting the first tie after detecting a loss of bi-directional connectivity between primary and backup redundant network access points during the primarily testing step. 
     
     
       17. The computer-readable medium of  claim 14  wherein the secondarily test comprises sending test request messages to a set of most recently accessed nodes on a network. 
     
     
       18. The computer-readable medium of  claim 17  wherein the set of nodes receiving request messages are determined by accessing a most recently used address list. 
     
     
       19. The computer-readable medium of  claim 17  wherein an odd number of secondary test request messages are sent out by the primary and backup redundant network access points. 
     
     
       20. The computer-readable medium of  claim 14  wherein the primarily test comprises sending a request message between from the primary network access point and the backup network access point and receiving a reply message within a time period. 
     
     
       21. The computer-readable medium of  claim 14  wherein the designating the current primary network access point is based upon tallied responses by the set of nodes, to which the redundantly connected node previously communicated, to test requests issued via the primary and backup network access points, respectively. 
     
     
       22. A node supporting redundant connectivity to an industrial local area network (LAN), the node comprising:
 a set of network access points for redundantly connecting the node to the industrial LAN; and 
 primarily testing bi-directional communicative connectivity, via the LAN, between a primary and a backup redundant network access point of the set of network access points; 
 secondarily testing, upon determining loss of communicative connectivity between the primary and backup network access points, connectivity between the set of network access points and a set of nodes on the LAN to which the redundantly connected node previously communicated; 
 designating a current primary network access point based upon results of the secondarily testing step; and 
 binding a first set of connections to the current primary network access point, wherein the first set of connections are re-bound to a newly designated current primary network access from a previous primary network access point in the event that the current primary network access point specified during the designating step differs from a previously designated primary network access point. 
 
     
     
       23. The node of  claim 22  wherein the secondarily testing step comprises determining a number of responses received by each one of the set of network access points and, upon detecting a first tie in the number of received responses after detecting loss of connectivity during the primarily testing step, designating a new primary network access point during the designating step in response to detecting the first tie. 
     
     
       24. The node of  claim 23  wherein the designating a new primary network access point step is performed only in response to detecting the first tie after detecting a loss of bi-directional connectivity between primary and backup redundant network access points during the primarily testing step. 
     
     
       25. The node of  claim 22  wherein the secondarily test comprises sending test request messages to a set of most recently accessed nodes on a network. 
     
     
       26. The node of  claim 25  wherein the set of nodes receiving request messages are determined by accessing a most recently used address list. 
     
     
       27. The node of  claim 25  wherein an odd number of secondary test request messages are sent out by the primary and backup redundant network access points. 
     
     
       28. The node of  claim 22  wherein the binding step is transparent to applications running on the node. 
     
     
       29. The node of  claim 28  wherein the primarily and secondarily testing steps are carried out transparent to applications executing on the node. 
     
     
       30. The node of  claim 28  wherein the primarily and secondarily testing steps are carried out transparent to network layer processes. 
     
     
       31. The node of  claim 22  wherein the primarily testing comprises sending a request message between from the primary network access point and the backup network access point and receiving a reply message within a time period. 
     
     
       32. The node of  claim 22  wherein the designating the current primary network access point is based upon tallied responses by the set of nodes, to which the redundantly connected node previously communicated, to test requests issued via the primary and backup network access points, respectively. 
     
     
       33. The node of  claim 22  wherein the primarily and secondarily testing steps are carried out via logical link control layer communication protocol components.